Making PastelView more Objc compatible.

[kgellci]

Currently PastelView is not fully objc compatible because of the Point enum.

I made several changes to make it compatible and maintain the full original functionality:

• Point enum renamed to PastelPoint and custom case with associated type removed.

• startPoint and endPoint properties are now CGPoint allowing for setting custom points without enum

• Added startPastelPoint and endPastelPoint properties to PastelView which will set the startPoint and endPoint CGPoint properties from their didSet methods.

• Changed method definition for setColors and addColor for better readability when using. *not needed for the objc support.

• Changed code in Readme to reflect changes.

With these changes, PastelView is fully usable in objc out of the box.

[cruisediary]

thank you @kgellci work fine :D 💯